A network engineer is implementing Layer 3 MPLS VPNs on Cisco IOS/IOS XE PE routers. Which PE-to- CE routing protocol requires a separate routing process to be created for each VRF?

Question

Options

• ARIPv2
• BOSPF
• CBGP
• DEIGRP

• A
  8% (3)
• B
  88% (35)
• C
  3% (1)
• D
  3% (1)

Explanation

OSPF is the only PE-to-CE routing protocol listed that requires a dedicated router ospf <process-id> vrf <vrf-name> instance per VRF - there is no address-family mechanism to consolidate multiple VRFs under a single OSPF process on Cisco IOS/IOS XE, making each VRF its own isolated OSPF domain.

Why the distractors are wrong:

• A. RIPv2 - uses address-family ipv4 vrf <name> under a single RIP process, so one process handles multiple VRFs.
• C. BGP - also uses address-family ipv4 vrf <name> under the single global BGP process; no separate process is needed per VRF.
• D. EIGRP - supports the same address-family model (classic or named mode), allowing one process to serve multiple VRFs via address-family ipv4 vrf <name> autonomous-system <AS>.

Memory tip: Use the acronym itself - OSPF = "One Separate Process (per) VRF". The O, S, and P in OSPF remind you that it's the outlier requiring a separate process for each VRF, while all the others can consolidate under address families.

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